Weird noise from engine block

[Ziox]

I have a worrying sound from my 1.6 Litre NB 2000 mx-5 107.000km (Timing belt changed at 80.000km at a workshop by previous owner) . I have searched a bit around after people with a similar problem but with no luck. So asking you clever people out there is my only solution other than opening the top cover. (or paying alot to a mazda workshop)

I tried to find the source of the sound with use of a stethoscope. (I tried: waterpump, alternator, steering pump and varius spots on the timing belt cover) I did find a spot where the sound i was looking for was amplified. The sound is coming from behind the timing belt cover near the crankshaft sprocket.



I can hear the sound when the engine is warmed up and can be heard best when idling.

Here is the sound: http://vocaroo.com/i/s0eWqhvLWxhQ

Need more info just ask.

[BoBo]

Your crank pulley key might be loose. Is your pulley wobbly? It kind of sounds like it but it could also be the bearing on your water pump.

[Ziox]

Here is a video:

[— kung fu jesus —]

I don't know this particular 1.6 variant well, but my first thought was front crankshaft seal. I mis-installed one on my b6 1.6. It was a little crooked. It started making noise and squealing a few months later, like a belt was going bad. It finally walked out and dumped oil on the floor of my garage.

The other thoughts were maybe something is making contact with the pulley, like one of the front engine covers. It also sounds vaguely similar to a failing air conditioning pump or bad air con pump clutch. Maybe a failing bering on the alternator. A hardened, aged accessory belt can also sing like that.

I also wanted to say EXCELLENT job documenting the sound and video!

[Ziox]

Thank you for your replies, I will hopefully get my parts this weekend to start removing the cover and top.

I did order..

For the job :
- Camshaft Timing Belt Kit, Genuine Mazda, 1.6 Mk1/2/2.5
- Camshaft Locking Tool, MX5 Mk1/2/2.5

Anything else i might buy when doing this?

Extra :
- Stainless Steel Scuff Plates, MX5 Mk2/2.5
- Aluminium Pedal Cover Set, Mazda MX5 Mk2/2.5

From: http://www.mx5parts.co.uk/

The problem is not yet solved so please, if anyone know of this problem -> Comment!

[— Malibu Q —]

Sounds like an external bearing. Check alternator, water pump, AC, power steer first by removing belts and spinning each one by hand. If they feel okay remove the front covers and look at the water pump and cam idler pulleys. Good luck.

[Ziox]

I believe it is the timing belt tensioner, because i did check alternator, waterpump and powersteer with a stethoscope and they all sound normal. Do anyone know how a bad tensioner sounds, and is it the same as mine? Like Malibu said, it does sound like a bearing, but if it had been the water pump i would have heard by putting the stethoscope at the waterpump sticking out of the engine.

[— Malibu Q —]

The tensioner and idler pulley have sealed bearings and would most likely sound like yours if faulty. I read the thread again and the cam idler pulleys sound like the most probable cause. ILM has them for about €50 for both.

[Ziox]

I did order a timing belt kit, which includes:

1 x Timing Belt
1 x Idler Pulley
1 x Tensioner Pulley
1 x Tensioner Spring
1 x Cam Cover Gasket

I will post a reply here if it works or not.

Thank you all for the helpful feedback!

[— kung fu jesus —]

You may be on to something with the tensioner. One could be bad or loose. I completely forgot about those. Those are parts I question when someone tells me they "changed the timing belt". Often, some just change the belt itself, especially if they plan to sell the car soon. They leave the rest of the parts for someone else to replace.